gro: Fix frag_list merging on imprecisely split packets

The previous fix ad0f9904444de1309dedd2b9e365cae8af77d9b1 (gro:
Fix handling of imprecisely split packets) only fixed the case
of frags merging, frag_list merging in the same circumstances
were still broken.

In particular, the packet headers end up in the data stream.

This patch fixes this plus another issue where an imprecisely
split packet header may be read incorrectly (this is mostly
harmless since it'll simply cause the packet to not match and
be rejected for GRO).

Thanks to Emil Tantilov and Jeff Kirsher for helping to track
this down.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 13 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 3337cf98f231..247f1614a796 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2391,7 +2391,8 @@ void *skb_gro_header(struct sk_buff *skb, unsigned int hlen)
                 return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
 
         return page_address(skb_shinfo(skb)->frags[0].page) +
-               skb_shinfo(skb)->frags[0].page_offset + offset;
+               skb_shinfo(skb)->frags[0].page_offset +
+               offset - skb_headlen(skb);
 }
 EXPORT_SYMBOL(skb_gro_header);
 
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e55d1ef5690d..67f2a2f85827 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2678,6 +2678,17 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
         p = nskb;
 
 merge:
+        if (skb_gro_offset(skb) > skb_headlen(skb)) {
+                skb_shinfo(skb)->frags[0].page_offset +=
+                        skb_gro_offset(skb) - skb_headlen(skb);
+                skb_shinfo(skb)->frags[0].size -=
+                        skb_gro_offset(skb) - skb_headlen(skb);
+                skb_gro_reset_offset(skb);
+                skb_gro_pull(skb, skb_headlen(skb));
+        }
+
+        __skb_pull(skb, skb_gro_offset(skb));
+
         p->prev->next = skb;
         p->prev = skb;
         skb_header_release(skb);